Knife sharpening mechanism

ABSTRACT

WHEN THE PRESSURE BETWEEN SAID KNIFE AND SAID SHOE EXCEEDS THE PRESSURE OF SAID BIASING MEANS URGING SAID SHOE TOWARD SAID KNIFE, SAID DETENT MEANS COMPRISING A FINGER ATTACHED TO SAID LOWER SHOE FOR ENGAGEMENT WITH A PLURALITY OF SERRATIONS ON A PIVOTAL ARM ON SAID CARRIAGE, SAID SERRATIONS BEING OF A CONFIGURATION TO PERMIT SAID FINGER AND SAID LOWER SHOE TO MOVE AWAY FROM SAID KNIFE BUT PREVENTING SAID LOWER SHOE FROM MOVING TOWARD SAID KNIFE WHILE SAID FINGER IS IN ENGAGEMENT WITH SAID SERRATIONS, AND CAM MEANS FOR PERIODICALL RESETTING SAID LOWER SHOE IN A DIRECTION TOWARD SAID KNIFE.   A KNIFE SHARPENING MECHANISM FOR A CUTTING MACHINE HAVING AN ELONGATED KNIFE COMPRISING A GRINDER CARRIAGE HAVING AN UPPER LEG AND A LOWER LEG, AN UPPER ENDLESS ABRASIVE BELT MOUNTED ON THE UPPER LEG, A LOWER ENDLESS ABRASIVE BELT MOUNTED ON THE LOWER LEG, DRIVE MEANS FOR DRIVING SAID BELTS, AN UPPER BELT GUIDING SHOE FOR HOLDING SAID UPPER BELT IN ENGAGEMENT WITH SAID KNIFE, A LOWER BELT GUIDING SHOE FOR HOLDING SAID LOWER BELT IN ENGAGEMENT WITH SAID KNIFE, BIASING MEANS FOR URGING SAID LOWER SHOE IN A DIRECTION TOWARD SAID KNIFE, DETENT MEANS FOR HOLDING SAID LOWER SHOE AGAINST MOVEMENT TOWARD SAID KNIFE AS SAID CARRIAGE MOVES LONGITUDINALLY OF SAID KNIFE WHILE PERMITTING SAID SHOE TO MOVE AWAY FROM SAID KNIFE

Feb. 6, 1973 F. G. CLARK KNIFE SHARPENING MECHANISM Filed July 15, 1971 3 Sheets-Sheet 1 INVENTOR.

FREDERICK G. CLARK ATTORNEYS Feb. 6, 1973 CLARK 3,714,742

KNIFE SHARPENING MECHANISM Filed July 15, 1971 3 Sheets-Sheet 2 g 26 f 27 l 20 I I I I FREDERICK G. CLARK 1973 F. G. CLARK 3,714,742

KNIFE SHARPENING MECHANISM Filed July 15, 1971 3 Sheets-Sheet 3 w T F 12.

INVENTOR.

FREDERICK G. CLARK ATTORNEYS United States Patent "ice 3,714,742 KNIFE SHARPENING MECHANISM Frederick G. Clark, Buffalo, N.Y., assiguor to Eastman Machine Company, Buffalo, N.Y. Filed July 15, 1971, Ser. No. 162,922 Int. Cl. B24b 19/00, 2/00 US. Cl. 51-246 8 Claims ABSTRACT OF THE DISCLOSURE A knife sharpening mechanism for a cutting machine having an elongated knife comprising a grinder carriage having an upper leg and a lower leg, an upper endless abrasive belt mounted on the upper leg, a lower endless abrasive belt mounted on the lower leg, drive means for driving said belts, an upper belt guiding shoe for holding said upper belt in engagement with said knife, a lower belt guiding shoe for holding said lower belt in engagement with said knife, biasing means for urging said lower shoe in a direction toward said knife, detent means for holding said lower shoe against movement toward said knife as said carriage moves longitudinally of said knife while permitting said shoe to move away from said knife when the pressure between said knife and said shoe exceeds the pressure of said biasing means urging said shoe toward said knife, said detent means comprising a finger attached to said lower shoe for engagement with a plurality of serrations on a pivotal arm on said carriage, said serrations being of a configuration to permit said finger and said lower shoe to move away from said knife but preventing said lower shoe from moving toward said knife while said finger is in engagement with said serrations, and cam means for periodically resetting said lower shoe in a direction toward said knife.

The present invention relates to an improved knife sharpening mechanism for cloth cutting machines in which the cutting is effected by a reciprocatory knife.

By way of background, the knife of the foregoing type of machine must be sharpened periodically. The sharpening is effected by running a grinder carriage longitudinally of the knife, the carriage mounting a pair of endless belts which are held in grinding engagement with opposite sides of the knife. The belts are located one above the other in substantially parallel planes so as not to interfere with each other during the grinding. In order for the side of the knife which is sharpened by the upper belt to be sharpened all the way to the bottom, the lower belt must be moved to a position below the lower end of the knife during a portion of the knife sharpening operation. Suitable mechanism has been provided in the past, as shown in US. Pat. No. 2,829,474, to prevent the lower belt from moving underneath the lower end of the knife where it could snag on the knife during upward movement of the carriage. However, this prior mechanism did not permit the lower belt to yield away from the knife. In addition, it has been found that the movement of the sharpening belts across the edge of the knife draws the carriage toward the knife in a direction which will grind a longer bevel on the knife. Since the carriage is supported in a cantilevered manner at the end of a link which becomes longer as the carriage moves toward the lower portion of the knife, and since the lower belt cannot yield away from the knife, the lower end of the knife tends to be sharpened with a progressively longer bevel because the cantilevered link will yield more as the carriage is supported by the progressively longer link. The longer bevel thus produced results in a curved shape on the lower end of the knife which is objectionable. It is with overcoming the foregoing deficiency of the prior types of sharpening devices that the present invention is concerned.

3,714,742 Patented Feb. 6, 1973 It is accordingly the object of the present invention to provide an improved knife sharpening mechanism for a cloth cutting machine in which the knife is sharpened substantially straight with a uniform bevel throughout its length notwithstanding that the sharpening mechanism is mouned in a cantilevered fashion-on the machine which would tend to cause it to sharpen the knife with a progressively longer bevel. Other objects and attendant advantages of the present invention will readily be perceived hereafter.

The improved knife sharpening mechanism of the present invention comprises a grinder carriage for movement longitudinally of the knife, an abrasive knife sharpening belt on the carriage, means for moving the belt transversely of the knife to thus sharpen the edge thereof, a belt guiding shoe on the carriage, biasing means for uring the shoe toward the knife to cause the belt to engage the knife, and detent means for holding the shoe against movement toward said knife as said carriage moves longitudinally of said knife while permitting said shoe to move in a direction away from said knife when the pressure between said knife and said shoe exceeds the pressure of said biasing means urging said shoe toward said knife. By means of the foregoing construction the carriage which is mounted in a cantilevered manner on the remainder of the machine will not produce a progressively longer bevel at the lower portions of its stroke. The various aspects of the present invention will be more fully understood when the following portions of the specification are read in conjunction with the accompanying drawings wherein:

FIG. 1 is a fragmentary side elevational view of the lower portion of a cloth cutting machine mounting the improved knife sharpening mechanism of the present invention;

FIG. 2 is a view of the knife sharpening mechanism taken substantially along line 22 of FIG. 1;

FIG. 3 is a cross sectional view taken substantially along line 3-3 of FIG. 2 and showing the detent structure in conjunction with other parts of the knife sharpening mechanism;

FIGS. 4 and 5 are schematic views showing the same manner in which the shoes are separated at the top of a sharpening stroke preparatory to resetting them;

FIG. 6 is a schematic view showing the manner in which the detent structure approaches shoe-disengaging position;

FIG. 7 is a view showing the detent disengaged at the top of the stroke;

FIG. 8 is a fragmentary enlarged view of a portion of FIG. 2 showing the structure for holding the lower shoe against approaching the blade during the knife sharpening operation while permitting it to move away therefrom;

FIG. 9 is a view similar to FIG. 8 but showing the lower shoe moved to a new position as a result of the carriage having moved to the left from the position which it occupied in FIG. 8;

FIG. 10 is a fragmentary enlarged view of a portion of FIG. 9 showing the detent structure in greater detail;

FIG. 11 is a view similar to FIGS. 8 and 9 but showing the shoes and the detent structure separated;

FIG. 12 is a fragmentary side elevational view showing the ideal contour of the knife after sharpening;

FIG. 13 is a fragmentary side elevational view of the lower portion of the knife with an undesirable curved portion thereon which is produced in the event that the lower shoe is not permitted to yield in the event the carriage moves to the left as shown in FIG. 9;

FIG. 14 is a perspective view of a portion of the detent structure which cooperates with the lower shoe; and

FIG. 15 is a perspective view of the lower shoe having a finger thereon which forms part of the detent structure.

The improved sharpening mechanism 10 of the present invention is adapted to be permanently mounted on cloth cutting machine 11 which includes a base 12 which is adapted to rest on a table and to be moved about underneath a stack or lay of cloth to be cut. Rigidly affixed to and extending upwardly from base 12 is a standard 13, the upper end of which supports a stationary frame 14 containing an electric motor (not shown) which reciprocates knife 15 in a vertical guide 16 mounted in standard 13 through a suitable driving mechanism (not shown). A presser foot 17 is rigidly secured to the lower end of bar 18 which extends vertically downwardly from frame 14 and is suitably mounted for vertical adjustment on the machine so as to set the presser foot 17 at different levels according to the thickness of the material which is to be cut. Normally the sharpening mechanism is held in an elevated position immediately underneath frame 14 during the cutting operation. However, it is periodically actuated when cloth is not being cut, so as to travel in a direction parallel to knife in a reciprocating manner from top to bottom thereof to sharpen the knife, and after such sharpening is completed it is again locked in position immediately under frame 14. Knife sharpening mechanisms of this general type and cloth cutting machines of this general type are shown in greater detail in U.S. Pats. Nos. 2,790,235, 2,829,474 and 3,350,818.

The knife sharpening mechanism 10 includes a carriage 19 mounted at the lower end of shaft 20 having right and left-handed threads 21 thereon. When it is desired to cause carriage 19 to move downwardly to effect a knife sharpening operation, a suitable linkage (not shown) is actuated to cause shaft 21 to move downwardly and thus carry carriage 19 with it. At the lowermost portion of its travel carriage 19 will reverse and move upwardly due to the action of the double thread 21. Guide bar 18 is received with a sliding fit in aperture 22 of carriage 19 to aid in stabilizing the carriage during its travel back and forth.

Carriage 19 includes a pair of legs 23 and 24 which lie at different elevations in substantially parallel planes and merge at their right ends into block 25 which is formed integrally therewith. Shafts 26 and '27, which are driven in opposite directions by the motor within frame 14, effectively have drive pulleys 28 and 29 afiixed to the lower ends thereof. A first endless belt 30 encircles pulley 28 and pulley 31 journalled on bracket 32 which is loosely mounted on leg 24 and biased to the left in FIG. 2 by a spring 33 which is interposed between the end 34 of the leg 24 and a tab 35 extending upwardly from the lower side 36 of the bracket, bracket 32 being held on leg 24 by tabs 37, 38 and 39 which are bent over the top of leg 24. A second endless belt '40 encircles drive pulley 29 and pulley 41 which is journalled on bracket 42 which is a mirror image of bracket 32 and is mounted for sliding movement on arm 23 and is biased rearwardly by spring 43 which is analogous to spring 33. Screws 44 and 45 limit the longitudinal movement of brackets 32 and 42 in both directions on legs 24 and 23, respectively, because they are engaged by tabs such as 37 and 38. A guide member 40 is attached to legs 23 and 24 by screws 23 and 24', respectively, and includes portions 41 which engage standard 13 with a sliding fit to stabilize carriage 19 during its reciprocating movement.

Belts 30 and 40, which include a coating of suitable abrasive material, are urged into contact with opposite sides of knife 15 by shoes 46 and 47, respectively, which are pivotally mounted on legs 24 and 23, respectively. More specifically in the foregoing respect, shoe 46 includes a longitudinal portion 48 having an end which is pivotally mounted on pin 49. A spring 50 has end 51 affixed to leg 24 and end 52 affixed to shoe 46 so as to bias it in a clockwise direction in FIG. 2. A block 53 is attached to shoe 46 by means of set screw 54 and a hardened insert '55 on block 53 presses on the rear side of band 30 to urge it into engagement with one side of knife 15.

Shoe 47 includes a central portion 56 which is pivoted at its left end to leg 23 by pin 57. A spring 58 has end 59 fixed to leg 23 and end 60 fixed to shoe portion 56 so as to bias shoe 47 in a counterclockwise direction about pin 57 in FIG. 2. A block 61 (FIG. 3) is secured to shoe 47 by means of set screw 62 and carries a hardened insert 64 thereon which engages the rear of band 46 so as to hold it in engagement with the side of knife 15 which is opposite to that engaged by belt 30. It can readily be appreciated therefore that belts 36' or 40 are driven by shafts 26 and 27, respectively, so as to grind a bevel on knife 15 as carriage 19 is moved longitudinally thereof.

As can be seen from FIGS. 2 and 3, belt 40* lies below belt 30. The reason for this is so as to permit each belt to lie at an optimum angle relative to the edge of the knife without interfering with the other belt. However, in order to sharpen the side of knife 15 engaged by belt 30 all the way to the bottom, belt 40 must at the lowermost portion of its travel lie below the lowermost end 64 (FIG. 1) of knife 15. As explained in certain of the above mentioned prior patents, shoe 47 must be held against pivoting to a position underneath the end 64 under the urging of spring 58 so as not to be caught thereon during the upward movement of carriage 19. This is accomplished by a detent structure which includes a finger 65 which is formed as an extension of shoe 47 (FIG. 12). Cooperating with finger 65 as the other part of the detent structure is an arm 66 pivotally mounted on pin 67 extending downwardly from portion 68 formed integrally with carriage block 25. Pin 67 extends through boss 69 at the end of central portion 76 of arm 66. A spring 71 has one end 72 hearing against block 25 and the other end 73 secured in aperture 74 of arm 66. This causes arm 66 to be biased in a counterclockwise direction about pin '67 in FIG. 2. Formed integrally with arm 66 is a platelike portion 75 having a series of vertically extending serrations 76 formed on the face thereof for engagement by the tip of finger 65. As can best be seen from FIG. 10, the straight side 77 of finger 65 engages one of the straight sides 71; of serrations 76 so as to prevent shoe 47 from plvotmgin a counterclockwise direction in FIG. 2 while arm 66 is 131' ased in a counterclockwise direction in engagement with the tip of finger 65. Therefore when the lower belt 40 goes below the lower end 64' of knife 15, shoe 47 will be prevented from pivoting underneath the blade. I

As can be visualized from the above description of shaft 20 in relation to the remainder of the machine, carriage 19 is supported in a cantilevered manner on shaft 20 relative to frame 14. Therefore, the further carriage 19 moves away from frame 14, the less support it Will have against movement from side to side in FIG. 1. In addition, as can be seen from FIGS. 2, 8 and 9, belts 3t) and 40 move in the direction of arrows 7'9 and '80-, re spectively. Because they are in frictional engagement with knife 15 which is stationary, carriage 19 will tend to move in the direction of arrow 81 (FIG. 9) as carriage 19 progressively moves lower in a downward direction relative to knife 15. If shoe 47 could not yield in a clockwise direction about pin 57 in FIG. 2, the lower edge of knife 15 would eventually assume a configuration such as 82 in FIG. 11 rather than the desired configuration 83 shown in FIG. 10 and the undesired configuration 82 could lead to inaccuracies in cutting. Accordingly, in view of the pivotal mounting of arm 66 in a biased manner by spring 71, as carriage 19 moves to the left in the direction of arrow 81 (FIG. 9), shoe 47 will pivot in a clockwise direction about pin 57 when the pressure between belt 40 and plate 15 exceeds the biasing force of spring 58. This yielding is permitted because the inclined face 84 of finger 65 will travel along one of the inclined faces 85 of serrations 76 in the manner of a ratchet so as to move to a position such as shown in FIG. 9 from the position shown in FIG. 8. In other words, the above described construction will permit shoe 47 to yield in a direction away from the knife as carriage 19 moves to the left in FIG. 1 to thereby prevent excessive wearing away at the lower portion of knife 15. It is also to be noted that this construction also prevents shoe 47 from pivoting underneath the end 64 of knife 15, as described in detail above.

It will be appreciated that the shoe 47 has to be reset periodically so as to be urged into engagement with the edge of knife 15 because if it were to remain in the position shown in FIG. 9, belt 40 would not engage the knife With sufficient force for effective sharpening. This is accomplished by means of a camming pin 87 extending downwardly from frame 14. As carriage 19 rises upwardly, camming surfaces 88 and 89 on opposite sides of pin 87 will engage faces 90 and 91 of arms 46 and 47, respectively, as they move from the position shown schematically in FIG. 4 to the position shown in FIG. 5. This will relieve the pressure of shoes 46 and 47 so that belts 30 and 40 will not press against the knife. Parenthetically, it is to be noted that this is the position (FIG. 11) which the shoes occupy when the sharpening mechanism is not in use so as not to interfere with reciprocation of blade 15. In this position the shoes will be biased against pin 87 under the urging of the springs 50 and 58 associated therewith. It is also to be noted that pin 87 has a cam face 92 thereon which is engaged by inclined surface 93 on portion 75 of arm 66 so that this arm will be cammed in a clockwise direction about pin 67 to occupy the position shown in FIG. 11 at the uppermost portion of carriage travel, and in this position finger 65 will no longer be in engagement with serrations 76. Upon downward movement of carriage 19, surfaces 90 and 91 will leave cam surfaces 88 and 89, respectively, prior to the time that surface 93 of arm 66 leaves cam surface 92. Thus, shoes 46 and 47 will be biased into engagement with opposite sides of knife 15 by their respective springs. Thereafter there will be disengagement between surface 93 and cam surface 92 and arm 66 will pivot in a counterclockwise direction from its position shown in FIG. 11 to its position shown in FIG. 8 to perform its dual function described above of holding shoe 47 against pivotal movement in a direction toward the knife while permitting it to move in a direction away from it as the carriage 19 moves to the left.

It can thus be seen that the above described knife sharpening mechanism is manifestly capable of achieving the above enumerated objects and while a preferred embodiment has been disclosed, it will be appreciated that it can otherwise be embodied within the scope of the following claims.

What is claimed is:

1. A knife sharpening mechanism for a cutting machine having an elongated knife comprising a grinder carriage for movement longitudinally of said knife, an abrasive knife sharpening belt on said carriage, means for moving said belt transversely relative to the edge of said knife to thus sharpen said knife, a belt-guiding shoe on said carriage, biasing means for urging said shoe in a direction toward said knife to cause said belt to engage said knife, and detent means for holding said shoe against movement toward said knife as said carriage moves longitudinally of said knife while permitting said shoe to move away from said knife when the pressure between said knife and said shoe exceeds the pressure of said biasing means urging said shoe toward said knife.

2. A knife sharpening mechanism as set forth in claim 1 wherein said detent means includes means for preventing said shoe from moving closer toward said knife once it has been moved to a predetermined position away from said knife.

3. A knife sharpening mechanism as set forth in claim 2 wherein said detent means comprises a finger secured to said shoe and an arm on said carriage having finger engaging means for engagement by said finger.

4. A knife sharpening mechanism as set forth in claim 3 wherein said finger-engaging means comprise serrations having differently inclined opposite faces to permit said finger to travel across said serrations in said direction away from said knife but preventing said shoe from traveling in said direction toward said knife.

5. A knife sharpening mechanism as set forth in claim 4- including means on said cutting machine for periodically resetting said shoe in a predetermined sharpening position at a predetermined portion of a sharpening stroke.

6. A knife sharpening mechanism for a cutting machine having an elongated knife comprising a frame for mounting said knife, a grinder carriage having an upper leg and a lower leg, an elongated link mounting said carriage in a cantilevered manner relative to said frame for moving said carriage back and forth along said knife from a position proximate said frame to a position remote from said frame, an upper endless abrasive belt mounted on said upper leg in transverse relationship to said knife, a lower endless abrasive belt mounted on said lower leg in transverse relationship to said knife, drive means for driving said belts, an upper belt guiding shoe for holding said upper belt in engagement with said knife, a lower belt guiding shoe for holding said lower belt in engagement with said knife, biasing means for urging said lower shoe in a direction toward said knife, and detent means for holding said lower shoe against movement toward said knife as said carriage moves longitudinally of said knife While permitting said shoe to move away from said knife when the pressure between said knife and said shoe exceeds the pressure of said biasing means urging said shoe toward said knife.

7. A knife sharpening mechanism for a cutting machine having an elongated knife as set forth in claim 6 wherein said detent means comprises a finger attached to said lower shoe, a pivotal arm on said carriage, and serrations on said pivotal arm for engagement by said finger, said serrations being of a configuration to permit said finger and lower shoe to move away from said knife while preventing said lower shoe from moving toward said knife while said finger is in engagement with said serrations.

8. A knife sharpening mechanism for a cutting machine having an elongated knife as set forth in claim 6 including cam means for periodically resetting said lower shoe in a direction twoard said knife when said carriage is in said position proximate said frame.

References Cited UNITED STATES PATENTS 2,748,473 6/ 1956 Carapucci 51-246 X 2,753,670 7/ 1956 Carapucci 51-246 2,829,474 4/1958 Clark 51-246 3,350,818 11/1967 Clark 51-246 3,548,495 12/1970 Baldwin et al 51-246 X OTHELL M. SIMPSON, Primary Examiner US. Cl. X.R. 51142 

